The present invention relates to phenol-functional resins cured with isocyanate cross-linking agents and more particularly to such a system which is curable in the presence of vaporous tertiary-amine catalyst.
Vapor Permeation Cure (VPC) has been proposed on a limited basis by the prior art. For example, U.S. Pat. No. 2,967,117 shows a coating composed of a polyhydroxy polyester and a polyisocyanate which are cured in the presence of a gaseous tertiary amine or phosphine. The polyester contains aliphatic hydroxyl groups and heating of the coated substrate at about 60.degree.-120.degree. C. prior to or concomitant with the vaporous tertiary amine exposure is taught in the specification and examples. U.S. Pat. No. 3,874,898 shows a coating composed of a polymer containing only isocyanate functionality which can be cured in the presence of a vaporous amine. VPC technology additionally has been used for curing foundry binder compositions of a phenol-aldehyde resin (U.S. Pat. No. 3,409,579). Relative to the benzylic ether phenolic resin disclosed therein, reference also is made to U.S. Pat. Nos. 3,485,797, 3,676,392, and 3,501,552. For coatings applications, a hydroxy functional polyester may be end-capped with hydroxybenzoic acid as taught in U.S. Pat. No. 3,836,491, a phenol reacted with an unsaturated fatty acid or the like as taught in U.S. Pat. No. 3,822,226, or an epoxy polymer capped with hydroxybenzoic acid as taught in U.S. Pat. No. 3,789,044. British Pat. No. 1,351,881 modifies a polyhydroxy, polyepoxy, or polycarboxyl resin with the reaction product of a phenol and an aldehyde. The reaction product is curable with an isocyanate cross-linking agent in the presence of a vaporous tertiary amine. British Pat. No. 1,369,351 proposes a hydroxy or epoxy compound which has been reacted with diphenolic acid. The resulting compound is curable with a polyisocyanate according to VPC techniques.
In commonly assigned application Ser. No. 06/252,844, filed Apr. 10, 1981, now U.S. Pat. No. 4,366,193, a vapor permeation curable coating composition based on catechol is disclosed. It is noted in such application that resorcinol and hydroquinone do not rapidly react with isocyanate curing agents in the presence of vaporous tertiary amine catalyst whereas catechol did rapidly react with isocyanate curing agents under such conditions. Such application further postulates that the position of the two hydroxyl groups ortho to one another permits hydrogen bonding interaction which accelerates the curing process. Unexpectedly, it has been determined that a particular substituted resorcinol will rapidly react in the vapor permeation cure coating process contrary to such prior teachings.